Assigning a new material to a face makes it transparent
I hope this helps others who run across this. This is a known issue when using multiple materials with a number of older GeForce and Quadro graphics cards.


  Blender Known Issue: Drawing error with multi-material object. Faces disappear or showing artifacts with 2 or more material slots applied to same object. When trying to use a second material or more on an object, the faces where it is applied become transparent or in some cases they are distorted as black rectangles that stretch to the origin (this second occurs above all with more complex models than a cube). It happens in Blender 2.81 as well as in Blender 2.82, but in Blender 2.80 there is no such error.


While the bug report lists multiple cards such as the ones below, the list is not exhaustive (my card for instance, GeForce 9800 GTX+, is not listed), the core issue is that the GPU has to be able to run NVIDIA drivers greater than v400. The highest driver that I can install is the GeForce v342.01 driver.


GeForce 210 
GeForce 410M 
GeForce GT 220 
GeForce GTX 275 
Quadro FX 3700 
Quadro FX 3800 
Quadro FX 4800


I can also confirm that as listed in the bug report, Blender 2.80 does work for me.